// Copyright (c) 2000 - 2007, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
//     * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// Modified by AOYAMA Kazuharu
//
// Produce stack trace

#include <QtGlobal>
#include <cstdint>  // for uintptr_t

#if !defined(Q_OS_WIN32)
#include <sys/mman.h>
#include <unistd.h>
#endif

#include "gconfig.h"
#include "stacktrace.h"

_START_GOOGLE_NAMESPACE_

// Given a pointer to a stack frame, locate and return the calling
// stackframe, or return nullptr if no stackframe can be found. Perform sanity
// checks (the strictness of which is controlled by the boolean parameter
// "STRICT_UNWINDING") to reduce the chance that a bad pointer is returned.
template <bool STRICT_UNWINDING>
static void **NextStackFrame(void **old_sp)
{
    void **new_sp = (void **)*old_sp;

    // Check that the transition from frame pointer old_sp to frame
    // pointer new_sp isn't clearly bogus
    if (STRICT_UNWINDING) {
        // With the stack growing downwards, older stack frame must be
        // at a greater address that the current one.
        if (new_sp <= old_sp)
            return nullptr;
        // Assume stack frames larger than 100,000 bytes are bogus.
        if ((uintptr_t)new_sp - (uintptr_t)old_sp > 100000)
            return nullptr;
    } else {
        // In the non-strict mode, allow discontiguous stack frames.
        // (alternate-signal-stacks for example).
        if (new_sp == old_sp)
            return nullptr;
        // And allow frames upto about 1MB.
        if ((new_sp > old_sp)
            && ((uintptr_t)new_sp - (uintptr_t)old_sp > 1000000))
            return nullptr;
    }
    if ((uintptr_t)new_sp & (sizeof(void *) - 1))
        return nullptr;
#ifdef __i386__
    // On 64-bit machines, the stack pointer can be very close to
    // 0xffffffff, so we explicitly check for a pointer into the
    // last two pages in the address space
    if ((uintptr_t)new_sp >= 0xffffe000)
        return nullptr;
#endif
#if !defined(Q_OS_WIN32)
    if (!STRICT_UNWINDING) {
        // Lax sanity checks cause a crash in 32-bit tcmalloc/crash_reason_test
        // on AMD-based machines with VDSO-enabled kernels.
        // Make an extra sanity check to insure new_sp is readable.
        // Note: NextStackFrame<false>() is only called while the program
        //       is already on its last leg, so it's ok to be slow here.
        static int page_size = getpagesize();
        void *new_sp_aligned = (void *)((uintptr_t)new_sp & ~(page_size - 1));
        if (msync(new_sp_aligned, page_size, MS_ASYNC) == -1)
            return nullptr;
    }
#endif
    return new_sp;
}

// If you change this function, also change GetStackFrames below.
int GetStackTrace(void **result, int max_depth, int skip_count)
{
    void **sp;
#ifdef __i386__
    // Stack frame format:
    //    sp[0]   pointer to previous frame
    //    sp[1]   caller address
    //    sp[2]   first argument
    //    ...
    sp = (void **)&result - 2;
#endif

#ifdef __x86_64__
    // __builtin_frame_address(0) can return the wrong address on gcc-4.1.0-k8
    unsigned long rbp;
    // Move the value of the register %rbp into the local variable rbp.
    // We need 'volatile' to prevent this instruction from getting moved
    // around during optimization to before function prologue is done.
    // An alternative way to achieve this
    // would be (before this __asm__ instruction) to call Noop() defined as
    //   static void Noop() __attribute__ ((noinline));  // prevent inlining
    //   static void Noop() { asm(""); }  // prevent optimizing-away
    __asm__ volatile("mov %%rbp, %0"
                     : "=r"(rbp));
    // Arguments are passed in registers on x86-64, so we can't just
    // offset from &result
    sp = (void **)rbp;
#endif

    int n = 0;
    while (sp && n < max_depth) {
        if (*(sp + 1) == (void *)0) {
            // In 64-bit code, we often see a frame that
            // points to itself and has a return address of 0.
            break;
        }
        if (skip_count > 0) {
            skip_count--;
        } else {
            result[n++] = *(sp + 1);
        }
        // Use strict unwinding rules.
        sp = NextStackFrame<true>(sp);
    }
    return n;
}

_END_GOOGLE_NAMESPACE_
